Portable computers are known applications for the use of batteries. Portable computers can have internal batteries wherein the battery is integrated into the body of the portable computer, although the integrated battery may often be detachable. Also, portable computers can have external batteries where the battery is external of the body of the computer.
A portable computer is generally provided with a power-in receptacle to allow the computer to be powered from an external power source. The external power sources can be any source of power for operation of the computer and also recharging of the internal battery. Such external power sources include AC domestic outlets, a car battery outlet or any other external power source. In the case where the battery is external, the battery supplies power to the computer by means of an electrically conductive lead which connects the external battery to the power-in receptacle of the computer.
Both internal and external batteries are generally rechargeable. Internal batteries typically remain within the computer during recharging. The power needed to recharge the internal battery enters through the computer power-in receptacle which is also occasionally referred to as the computer power input receptacle.
External batteries can be recharged by means of an electrical lead extending from the external battery to the external power source, generally through an adapter. The external batteries may comprise an individual battery or a combination of batteries in a battery pack. While any type of external battery can be used, rechargeable lithium batteries are often used in electronic devices requiring a steady and reliable source of electrical energy. The essential components of a rechargeable lithium battery are an anode or negative electrode, a cathode or positive electrode and a lithium ion conducting non-aqueous electrolyte. The anode active component of a rechargeable lithium battery is a substance which is capable of inserting or intercalating lithium ions when the battery is charged and releasing lithium ions when the battery is discharged. The cathode active component of a rechargeable lithium battery is capable of incorporating lithium ions reversibly, whereby the lithium ions are released when the battery is charged and are reincorporated in the cathode active component on discharge. The electrolyte of a rechargeable lithium battery is usually a non-aqueous electrolyte, most commonly a solid or liquid polymer bearing a lithium compound having dissociable lithium ions, or a microporous polymer which has been impregnated with an organic liquid having a lithium salt dissolved therein, or any non-aqueous substance that is capable of conducting electricity by means of movement of lithium ions. The cathode active component is commonly a lithium containing chalcogenide, most frequently a lithium containing transition metal oxide.
It is apparent that by having an electrical load, such as a portable computer, powered by means of two sources, either external power sources or batteries, the user has a great deal of flexibility as to use of the electrical load. In the case where the electrical load is a portable computer, this combination of batteries and external power sources provides great flexibility to power the portable computer. For example, the portable computer may be powered by means of the external power source in an office environment where an external power source, such as an electrical wall outlet, is available. At this time, it may also be convenient to charge the internal battery so that it will be fully charged and available for further use. However, when an external power source is unavailable or inconvenient, an external battery pack may be used to power the portable computer.
It is known for portable computers to have more than one rechargeable battery in order to provide an extended mobile operating time to the computer. U.S. Pat. No. 5,818,200 teaches a dual smart battery detection system for portable computers where only one of two internal battery packs is charged or discharged at any one time. U.S. Pat. No. 5,955,867 teaches dual battery pack charging in a computer system where simultaneous recharging of both battery packs can occur once each battery pack has reached a predetermined charge level. U.S. Pat. No. 5,666,066 teaches sequential charging and discharging of batteries located within a computer. U.S. Pat. No. 5,976,720 discloses a battery pack with circuitry that protects the components from damage due to shorting and/or thermal overload.
However, in situations where only a single AC adapter is available, which is the common situation, it has not been possible in the past to recharge the external battery pack while simultaneously operating the electrical load, such as the portable computer. Similarly, in cases where the electrical load has an internal battery, it has not been possible to charge both the external battery pack as well as the internal battery with a single AC adapter. This has been the case, in part, because the voltage supplied by the AC adapter from an external power source will typically be matched to the voltage needed by the computer. The voltage needed by the computer is often higher than that suitable for charging the external battery. This has effectively prevented simultaneously supplying power from an external power source to both the external battery and the computer, either to operate the computer or charge the internal battery.
Accordingly, there is a need in the art for a device and method to simultaneously provide power from an external power source to both an external battery and an electrical load, such as a portable computer. In addition, there is a need in the art for a device and method to permit simultaneously charging an external battery pack and a battery pack internal to a personal computer from a single AC adapter.